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Beach rover uncovers Mars’s ancient oceans

By David L Chandler

The layers merge together to the left of this 4cm-wide image, indicating ancient underwater ripples

(Image&colon; NASA/JPL/Cornell/USGS)

The landing site of the Mars rover Opportunity was once the shore of a shallow, salty sea, NASA scientists have declared. The weight of evidence now gathered makes the conclusion unequivocal, they say.

It is the first time direct evidence has been found that a body of standing, liquid water ever existed on the surface of Mars. Many planetary scientists have long believed that was the case, but having solid proof on the ground will change how future exploration of the red planet proceeds, as ideas about its potential for life.

NASA is jubilant about the success. The team has “accomplished something that we dared only dream of”, said NASA chief Sean O’Keefe, while chief scientist Ed Weiler said the results are ” beyond our wildest expectations”.

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The clinching factor was the observation of distinctively curved lines of sediment, the result of the gentle sweeping motion of a current of water. Material deposited by wind shows quite distinctly different patterns.

Although the team had collected these images almost three weeks ago, they said, they decided to take the extra step of sending it out for peer review by specialists in the field of marine sedimentology who were not involved in the research. After two weeks, the reviews came back uniformly positive.

Finding fossils

Furthermore, although nobody is claiming to have found any signs of life, the scientists have now begun talking openly about the possibility of finding fossils in the kind of rocks Opportunity is studying.

“If you have an interest in finding fossils on Mars, this is the place you should go,” said Weiler, at Tuesday’s press conference at NASA headquarters in Washington, DC.

Steve Squyres, the rover mission’s chief scientist, emphasised the difference between this finding and the report on 2 March that the Martian soil had contained water.

“It’s like the difference between water you can draw for a well, versus water you can swim in,” he said. “Opportunity is now parked on what was once the shoreline of a salty sea on Mars.”

Northern ocean

One word about Opportunity’s landing site that no-one is using is “lake.” Unlike the twin rover Spirit’s landing site at Gusev crater, there is no obvious rim that could have contained a lake.

The chemical and mineral evidence also points very strongly toward extremely salty, briny water, perhaps part of a very large body of water. This might be the northern ocean some researchers have said once existed on Mars.

Further exploration by Opportunity could help to answer another crucial question&colon; how long did this salty sea exist?

Opportunity emerged from the 22-metre crater called Eagle on Monday, to see an incredibly smooth, rippling plain. It will now head rapidly across the 750 metres to a 200-metre crater, where tens of metres of sediments are likely to be exposed, providing a peek into the much longer-term history of water on Mars.

But, as of Tuesday, the fact that bodies of liquid water existed on Mars is no longer in dispute. Now, it is just a question of when, and where, and for how long.